1. Field of the Invention
This invention pertains to a compressed gas pressure regulator having an adjustment limiter.
2. Prior Art
The prior device is disclosed and fully described in R. T. Cornelius U.S. Pat. No. 2,981,280 of Apr. 25, 1961. This regulator has been extremely successful in commerce and is widely used by retailers of soft drinks and beer throughout the United States and other countries of the world. The regulator is typically used on metal bottles of high pressure carbon dioxide which have a bottle or supply pressure in the range of 700 to 1200 PSI at normal ambient temperatures. The regulator has been made in several models; for example, it has been made available in low pressure, medium pressure and high pressure variations. A typical low pressure regulator will be intended for beer and have an adjustable regulatable output pressure range of 0-60 PSIG; a medium pressure regulator for carbonation of cold soft drinks will have an adjustable regulatable output pressure range of 0-100 PSIG; and a high pressure regulator for carbonation of a warm soft drink supply will have a regulatable output pressure range of 0-160 PSIG.
It will be appreciated that beverage retailers hire many part-time and relatively untrained employees; many times they will be students or people working part-time on weekends or evenings. For the most part these people are insufficiently trained or not knowledgeable in the precautions required in the handling of compressed gases. Many times the retailer and/or his employee will completely ignore the instructions given with respect to the usage of compressed gas equipment.
The problem that has arisen is that the user of the regulator will attempt to adjust the regulator to give an output or regulated pressure in excess of what the device was intended for. The easiest way for these people to do this has been to go to a toolbox and get a longer screw than the adjusting screw supplied with the regulator and to install this longer screw and then excessively compress the spring to attain a higher output pressure. The extreme example is substitution of a hex head cap screw and usage of a wrench to tighten the cap screw down on the spring.
It is a normal and accepted commercial practice to manufacture and sell regulators with an adjusting screw precisely of the right length so that it is impossible to bottom out or compress the spring to solid height. However, regulator owners and/or users remove the manufacturer's adjusting screws and substitute their own screws. Further, it is an accepted commercial practice to provide an external lock nut on a pressure adjusting screw precisely as is shown in U.S. Pat. No. 2,981,280 and in fact this construction is presently specified by the dominant and largest soft drink company in the world as an equipment standard for its bottlers to comply to. With this construction the owner/user will many times remove the lock nut, thereby increasing the effective length of the adjusting screw to a length enabling solid compression of the diaphragm spring. It will be apparent that it is in pure defiance of common sense that individuals change the construction of the adjusting screw as they see fit.
The most serious result of this practice is that the pressure spring is collapsed to its solid height and the regulator valve is held open and cannot close because the spring no longer functions. Further, the relief function of the regulator in U.S. Pat. No. 2,981,280 will no longer operate because the valve stem is positively retained against the valve and the relief port cannot open. When the pressure regulator valve is held open, the full pressure of the supply bottle is applied to the beverage dispensing system. The typical beverage system has a working pressure in the range of 25-150 PSIG and the application of approximately 1,000 PSI results in a bursting of the equipment. This problem is aggravated by regulator users and owners who do not replace damaged or inoperative pressure gauges and therefore the indicator dials are inaccurate or do not work at all. As an example, if a user has an almost empty gas bottle, he may excessively tighten the adjustment screw and hold open the regulator valve. The proper output pressure would still not be attained because the bottle pressure is almost depleted. The regulator user then puts the regulator on a new bottle, forgets to back off the regulator adjustment and opens the master on-off valve on the gas bottle. The full bottle pressure is applied to the dispensing system and the system bursts at one of its weakest points. The result at the very best is a horrible mess with beverage blown over the area immediate to the bursting. More serious is the economic damage and most serious would be personal injury.
Another situation is where the gas bottle goes empty and the regulator user, in attempting to get the desired output pressure, bottoms out the spring and opens the regulator valve. The beverage, be it soft drinks or beer, can then backflow through the regulator and into the gas bottle. Obviously, the gas bottle is then contaminated and the life expectancy of the bottle may be reduced due to corrosion from the contaminants.